Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!oakhill!jeff
From: jeff@oakhill.sps.mot.com (Jeff Enderwick)
Newsgroups: comp.arch
Subject: Error magnitude in i860 fp divide.
Message-ID: <1991Jun21.203429.20415@oakhill.sps.mot.com>
Date: 21 Jun 91 20:34:29 GMT
Reply-To: jeff@otis.sps.mot.com (Jeff Enderwick)
Organization: Motorola Inc., Austin, Texas
Lines: 14


	I'm looking at an old i860 manual, sections 9.2 and 9.3. It appears
	that they propose fp division via reciprocal approximation and
	multiplication. The manual states that "Worst case error is about 
	two least-significant bits", for both SP and DP. I've tried doing
	some error analysis, and I can't figure out how they came up with
	a maximum error figure that small. 

	Does anyone know how to show this result, or does anyone know the
	number for the i860 applications group ?


	Jeff Enderwick
	jeff@otis.sps.mot.com